In general, machine tool damage (such as wear and defects) are thought to depend on the material and shape of the tool, the magnitude of cutting resistance to be acted on the tool in cutting, and other factors. When the tool is damaged quickly, that is the tool life is short, machining quality is disadvantageously unstabilized. Moreover, the tool is required to be exchanged often, thereby disadvantageously degrading machining efficiency.
Thus, conventionally, cutting tools with high wear resistance have been diligently and continuously developed, in view of structural stiffness in addition to their material and shape. Also, machine tools have been improved everyday to stabilize a machining environment, such as stiffness, based on the machine tools in order to achieve stable machining. Furthermore, regarding a machining method, as disclosed in the Japanese Unexamined Patent Application Publication No. 2003-170333, an attempt has been made to reduce wear and damage of a tool by decreasing fluctuations in cutting resistance during machining.
Incidentally, in the machining method disclosed in the Japanese Unexamined Patent Application Publication No. 2003-170333, a feed path of the tool capable of reducing fluctuations in cutting resistance during machining is generated, and the tool is moved along the path, thereby reducing wear and damages. Specifically, this feed path is generated by providing a geometrical restriction on each of two geometrical variables, that is, a maximum chip thickness before cutting and a cutting arc length of a tool interference part, so that these geometric variables each have a constant value at each part of the feed path irrespective of the location, the geometric variables being represented by a projected portion obtained when an interfering part between a workpiece and an end mill tool occurring due to a motion of a unit amount of the end mill tool is projected onto a machining plane along a rotation axis.